The present invention relates to a method and apparatus for etching a workpiece having a multilayer structure using a parallel-plate type gas plasma etching apparatus.
The use of a parallel-plate type gas plasma etching apparatus has been known in the art for etching a material with high precision. With such an apparatus, the choice between the anode and the cathode coupling mode is dependent on the frequency of the rf power to be used. For example, if the frequency of the rf power is 13.56 MHz, the rf power is applied either to the one of the electrodes on which the workpiece is disposed (the cathode coupling mode) or to the opposite electrode (the anode coupling mode). For frequencies of 400 kHz or lower, the anode coupling mode is usually employed.
In a case of the plasma etching of a workpiece having a multilayer structure, it is required that the etch rate of the material to be etched E(E) be high enough practically with respect to the etch rate of an underlying layer E(u) to obtain a high etch rate ratio R(E/u)=E(E)/E(u).
An object of the present invention is to provide a method with which a workpiece having a multilayer structure is etched using a parallel-plate type gas plasma etching apparatus in which a high etch rate ratio R(E/u) is realized.